In association with the spread of a CATV (Community Antenna Television) and a satellite broadcasting, the number of channels which can be set in a television receiver has been increasing. In the television receiver which can perform a multi-channel reception as mentioned above, in order to preset channels which can be received, an automatic programming process is executed when a television set is purchased.
When the automatic programming process is executed, the channels are scanned, whether a reception signal can be obtained or not is determined on each channel, and the receivable channels are preset. By performing a channel search and presetting the receivable channels as mentioned above, after the channels were preset, the channels are switched to only the preset channels. Even in case of a television receiver which can perform the multi-channel reception, the channel selection can be easily performed.
As mentioned above, in the automatic programming process, the channels are scanned and whether the reception signal is obtained or not is determined on each channel. Therefore, there is a case where the receiver is temporarily set to a channel having no signal.
However, when the receiver is temporarily set to a channel having no signal, a problem that a display on the screen is disturbed occurs.
That is, a display generating circuit to perform the screen display generates a display signal on the basis of a sync signal extracted from the reception signal. Therefore, when the receiver is temporarily set to a channel having no signal during the execution of the automatic programming process, a disturbance occurs in the sync signal and the screen display is disturbed.
Particularly, when a some signal exists at the same frequency as that of the set channel, this signal is received and there is a case where such a channel is erroneously preset as a channel having the signal by the automatic programming process.
In such a case, the preset of the erroneous channel can be erased by a channel erasing/adding process after that. However, when the receiver is set to the channel having no signal, the screen display by the channel erasing/adding process is disturbed, the display of the set channels cannot be known, and the erase of the preset cannot be easily performed.
To prevent such a situation, when the automatic programming process is executed, a method of muting a video signal and performing a screen display on a muting picture plane is considered. By muting the video signal as mentioned above, since the disturbance of the sync signal is eliminated, the disturbance of the display is eliminated.
However, when the video signal is muted, a video image of the received channel can not be seen during the execution of the automatic programing process and the channels to be preset cannot be confirmed.
It is, therefore, an object of the invention to provide a television receiver, a method of setting a reception channel, and an image display method, in which during the execution of an automatic programing process such that channels are sequentially scanned to thereby determined whether they can be received or not and the numbers of the channels which can be received are set, a disturbance of the screen display is eliminated and, even during the execution of the automatic programing process, a received picture plane can be confirmed.
Another object of the invention is to provide a television receiver, a method of setting a reception channel, and an image display method, in which during the execution of a channel erasing/adding process such as to add or erase a channel number, a disturbance of the screen display is eliminated and, even during the execution of the channel erasing/adding process, a received picture plane can be confirmed.